As our understanding of epigenetics expands, it is becoming clear that players in this field are potential targets for drug development. This area of epigenetic therapy has established applications for the treatment of cancer and neurological diseases. We have been involved in this field for a number of years and have performed high-throughput screens to identify the first small molecule inhibitors of protein methyltransferases. These methyltransferases target multiple substrates, and thus regulate many arms of an epigenetic pathway. The methylation of different substrates often generates docking sites for effector protein that harbor domains (chromo, tudor, PHD, MBT and ANK repeats). We hypothesize that by inhibiting specific protein-protein interactions we will be able to develop compounds that block a single arm of an epigenetic pathway. The specificity attained by blocking a single protein-protein interaction will be far greater than that attained by blocking the enzyme that regulates one of many interactions. Low-affinity protein-protein interactions (Kd in the single- to double-digit micromolar range) such as those discussed here have been very difficult to assay by traditional techniques such as fluorescence polarization or fluorescence resonance energy transfer. We have solved this problem by developing a sensitive chemiluminescence-based assay, which serves as the starting point for this project. Here we plan to perform screens to identify lead compounds that can block methyl- dependent protein-protein interactions, which can be used as probes to analyze these methyl-driven interactions and perhaps even developed into targeted epigenetic therapies. ) PUBLIC HEALTH RELEVANCE: Epimutations, unlike genetic mutations, can be reversed by chemotherapeutic intervention, which makes epigenetic therapy conceptually extremely appealing. Drug therapies that target chromatin have been touted as the next emerging frontier for the treatment of cancer and neuronal-based diseases. In this study, we will identify small molecules that will prevent these epimutations from being read.